The present invention relates to a protection device for protecting an electrical connector from electromagnetic interference, the connector including a body made of a plastics material having a front face serving to co-operate with a removable plug and a connection side face touching a printed circuit board.
The device of the invention may be used in particular for protecting from electromagnetic interference a connector of known type such as DIN Standard F48 or E48 connectors which are in common use for interconnecting printed circuits with control or power supply cables, e.g. in an installation having electronics cards carried by a rack module on board a motive power unit of a rail vehicle.
In the prior art, in particular in compliance with Standard Deutsches Insitut fxc3xcr Normung eV (DIN) 41612/International Electrotechnical Commission (IEC) 603-2 and using DIN F48 or E48 type connectors, it is known that is possible to protect electronics cards from electromagnetic radiation by using removable plugs that are shielded by means of conductive cladding of the xe2x80x9cZamakxe2x80x9d type. Unfortunately, such a solution suffers from the drawback of significantly increasing the overall size of the plug, which makes it necessary to reduce the number of contacts available in the plug for cards at the same pitch. In addition, such a shielded plug is much more costly to manufacture than a conventional plug made of plastic, and it is much heavier, which gives rise to additional constraints, in particular in terms of vibration behavior. Another drawback with shielded plugs is that the magnetic protection disappears whenever the plug is removed, even though, in some uses, a plug is necessarily plugged in only occasionally, in particular for maintenance or testing of certain electronics cards. Such a solution makes it necessary to leave a shielded plug connected permanently in order to guarantee that the electronics card is magnetically protected, which gives rise to increased equipment cost.
An object of the present invention is thus to remedy the various above-mentioned drawbacks of the prior art.
To this end, the invention provides a protection device for protecting an electrical connector for a printed circuit board from electromagnetic interference, the connector including a body made of a plastics material having a front face serving to co-operate with a removable plug and a connection side face touching the board of the printed circuit, the connector including a plurality of contacts, each of which has one end in the form of a spike that projects from the connection side face, the spikes being inserted through holes in the board for the purpose of electrically connecting the contacts to one or more conductor tracks of the printed circuit, said protection device comprising a first shielding element extending facing the side face of the connector that is opposite from the connection side face, and continuing facing the rear face of the connector so as to come into contact with a grounding conductor track of the board of the printed circuit, and a second shielding element mounted on that face of the board of the printed circuit which is opposite from its face in contact with the connector, and extending facing said connection side face, the second shielding element being in contact with a conductor track connected to the grounding track of the printed circuit so as to be electrically connected to the first shielding element and so as to form a potential cage.
In particular embodiments, the protection device of the invention may comprise one or more of the following characteristics, taken either in isolation or in any technically feasible combination:
the first shielding element comprises a metal element that is substantially uninterrupted and that extends facing the rear face of the connector to the vicinity of the board of the printed circuit, that edge of the metal element which is adjacent to the printed circuit board being provided with spikes that are inserted into plated through holes in the board of the printed circuit, which holes are in contact with the grounding track of the printed circuit.
the first shielding element is constituted by a metal angle bracket having a branch extending facing that side face of the connector which is opposite from the connection face, and a branch extending facing the rear face of the connector;
the connector includes a plurality of rows of contacts including a top row of contacts that is the row furthest from the board of the printed circuit and that has a rear portion extending perpendicularly to the board of the printed circuit at the rear face of the connector so that the ends of the contacts, which ends are in the form of spikes, penetrate into plated through holes in the board, the top row of contacts being used to form a first shielding element by connecting the spikes of the contacts of the top row to the grounding conductor track;
the first shielding element is formed by a metal sheet co-operating with the top row of contacts, said metal sheet extending facing that side face of the connector which is opposite from the connection face, and having a curved-over end coming into contact with said top row of contacts;
the second shielding element is constituted by a metal sheet which is in contact with a track disposed at the surface of the board and connected to the grounding track to which the spikes of the first shielding element are connected;
the printed circuit board is designed to equip a rack module provided with many electronics cards disposed side-by-side, the metal sheet that constitutes the second shielding element being provided with resilient tongues projecting sideways from the fascia element so as to establish electrical contact with the shielding elements of a connector carried by an adjoining electronics card that is held in the rack module;
a fascia element is mounted on said connector, said fascia element being provided with fixing means for mounting the printed circuit on a rack module;
the fascia element supports the metal elements of the first shielding element;
the connector complies with DIN Standard type F48;
the fascia element includes an electrically-conductive body surrounding all four side faces of the connector, the fascia element including a top wall adjacent to that side wall of the connector which is opposite from its connection face, and a bottom wall adjacent to the board of the printed circuit, the walls respectively participating in forming the first and second shielding elements;
the first shielding element is formed by the top wall and by a metal angle bracket mounted against the top wall, said angle bracket having a branch extending facing the rear face of the connector and being fixed to the top wall so that electrical continuity exists between the angle bracket and the top wall;
the first shielding element is formed by the top wall and by a metal sheet mounted against the top wall, the metal sheet co-operating with the top row of contacts and having a curved-over end coming into contact with said top row of contacts;
the second shielding element is formed by the bottom wall which is in contact with a conductor track disposed at the surface of the board of the printed circuit and connected to the grounding track to which the spikes of the first shielding element are connected;
the printed circuit board is designed to equip a rack module provided with many electronics cards disposed side-by-side, and the bottom wall of the fascia element is provided with resilient tongues that project sideways from the fascia element so as to establish electrical contact with the shielding elements of a connector carried by an adjoining electronics card that is held in said rack module;
the fascia element is a xe2x80x9cZamakxe2x80x9d casting, and
the connector complies with DIN Standard type E48.